Method of manufacturing valves



May 17, 1938. 5. J. NORDSTROM METHOD OF MANUFACTURING VALVES Filed May ,12, 1936 INVENTOR SvanJ. Ncaosraon W ZX W A ORNEYS Patented May 17, 1938 PATENT OFF-ICE METHOD OF MANUFACTURE; VALVES Sven J. Nordstrom, Piedmont, Calif., assignor to Merco Nordstrom Valve Company, Pittsburgh, Pa., a corporation of Delaware Application May 12, 1936, Serial No. 79,399

7 Claims.

This invention relates to a novel method for the manufacture of irregular shaped containers or casings for high pressure service such as valves and the products formed thereby, and has particular application to the manufacture of plug valves.

In the manufacture of plug valves which will be discussed by way of example, particularly plug valves of the lubricated type, it is usual to com- 10 pletely assemble the valve with the plug carefully lapped into its seat and test it at double its, rated maximum working pressure before the .valve is shipped from the factory. As a result of such tests, it has been found, particularly with the types of valves designed for high pressure work, that after'the test pressure was ap plied to the assembled valve, permanent changes in form of the valve body frequently resulted.

Thus in a valve which was virtually finished and otherwise ready forsale, the accurate contact between the plug and body seating surfaces which hadbeen so carefully produced would be destroyedand an examination would show that the plug would then be hearing heavily on the body over certain areas and would be out of contact .with the body over other areas with resultant deleterious efiects such as hard-turning,

impairment of the seal, and non-uniformity of lubricant distribution in the case of lubricated valves. In such cases it, has been necessary to :eggind the plug, into its seat and repeat the According to the present invention this dim-- culty is obviated by subjecting a valve body preterably immediately prior to the final machining operations to an internal pressure substantially greater than the maximum rated working pressure of the valve to prestress the valve body, this prestressing treatment being carried out be- .m fore the final machine cut of the valve seat is made. After the valve has been subjected 'to this prestressing treatment, the final machine cut of the valve seat is made, the valve plug is care- 55 be substantially in excess of the test pressure or' any other pressure which the valve may be subjected to in service, and the duration of the treatment may vary from about two to. five minutes or longer.

It is my theory in explanation of this inven- 5 tion, that due to the non-uniform thickness and irregular shape of the walls of such a container or casing as a valve body, when the valve heretofore has been subjected to a test pressure, certain portionsof the valve walls were stressed be- 10 yondtheir elastic limit thus causing the valve body to take a permanent set by cold fiow. This did not materially weaken the valve because only sufiicient distortion occurred to substantially equalize the internal stresses, or at least equalize 15 them at the test pressure. Accordingly, in subjecting the valve bodies to a prestressing pressure higher than the test pressure, I believe I produce an equalization of the internal stresses up to the prestressing pressure applied so that no dis- 0 tortion or permanent set of the valve willthere after occur when the valve body is subjected to 3 a pressure up to the prestressing pressure.

In general, the prestressing pressure may be from about 16% per cent to 25 per cent in excess of the final test pressure which is to be applied to the valve, or about 133 per cent to I50 per cent in excess of the rated working pressure of the valve. The duration of the pressure treatment required may be determined by securing an 30 extensometer gauge to the valve which registers elongations in units of one ten-thousandths of an inch, and observing the movement of the gauge, the treatment being completed when substantially no further movement of the gauge in- 35 dicator is apparent. The. valve body is then removed from the pressure treating machine and the tapered seat is machined to final dimension.

It is preferred that the machining before treat- *ing allow approximately 0.010 inch to 0.015

inch to be removed after the prestressing operation. The valve plug is then insetted in the ,valve seat with a grinding compound and is carefully ground into the seat to an accurate'fit.

The valve isthen finally assembled and tested. 15

The invention may be illustrated by several examples. A cast steel valve intended for a' working pressure of 1200 pounds per square inch would be subjected to a test pressure of twice its working pressure or 2400 pounds per square inch after it is finally assembled.- According to the present invention I subject the rough valve body to a prestressing pressure of 3000' pounds per square inch for aperiod of about three minutes, and thereafter complete the u 0 l9 at one end and to a piston (not shown) in the machining and lapping of the valve body. In the case of a valve intended for a working pressure of 2000 pounds per square inch the test pressure would be 4000 pounds per square inch, and a prestressing pressure of 5000 pounds per square inch could be employed for about four minutes. In the case of a valve intended for a working pressure of 3000 pounds per square inch the test pressure would be 6000 pounds per square inch and a prestressing pressure of 7000 pounds per square inch for about five minutes would be employed.

It is therefore an object of the present invention to provide a novel method of manufacturing containers or vessels of irregular shape designed to resist relatively high pressures contained therein such, for instance, as valve bodies, such bodies after being treated according to my method being characterized by a permanent set below a predetermined pressure and at the work- 'ing pressure or pressures for which the container is designed.

A further object of my invention is a novel container or vessel t9 retain substances under pressure, such for instance, as a valve body, wherein the body is set permanently as regards the intended working and testing pressures and no cold fiow occurs under such pressures to deform the body.

Still a further object of my invention is the provision of novel apparatus for prestressing a valve body or like container designed to contain substances under pressure wherein the degree of prestressing may be accurately controlled.

Other objects and advantages of my invention will be apparent from the following description and reference to the accompanying drawing wherein:

Figure l is a side elevation of a preferred apparatus for carrying out my new method.

Figure 2 is a vertical section of a valve body to be treated.

Referring to the accompanying drawing, a preferred embodiment of 'my treating apparatus comprises a heavy bench I having a stationary head 2 securely bolted thereto, and amovable head 3. The head 2 has a plurality of undercut radial slots 4 which receive the heads of suitable bolts by which the hollow extension 5 is secured thereto. The slidable head 3 has a face plate 6 with similar undercut slots whereby the extension I is secured thereto. The extension i has a plate 8 for closing the end of the valve 10 to be treated, and the opposite end of the valve abuts the face of hollow extension 5, suitable, interposed to prevent leakage gaskets being The movable head 3 is guided on blocks ll slid able on the edge l2 of the bench. A cross head i3 is similarly slidable on the edge or tracks I2 and is connectedto the head 3 by a screw l0 and rotatable collar I5 havinga handle is extending therefrom bymeans of which the distance between cross head l3 and head 3 may be accurately adjusted. Two links it and I! are swiveled to the cross head l3 and fixed head l8 and are pivotaliy connected by a pivot pin 09. A hydraulic cylinder 2i is plvotally secured to *extensions 22 depending from the bench on both sides, and a piston rod 23 is secured to the pivot cylinder 2| at its other end. Inlet pipe 20' and outlet pipe 25 lead from a four way valve 26, connected to a supply pipe 21 which conducts kerosene, water, or othr fluid under pressure for operating the hydraulic pistonand connected to a suitable outlet.

The valve is subjected to internal pressure by liquid introduced through pipe 20 to the hollow extension 5, suitable valves (not shown) being providedto control the admission of the liquid.

, The valve casing I0 has a transverse passageway 3| therethrough for flow of fluid and a taperedseat 32 which is shown in exaggerated outline as having-a rough machined surface. An extension of the casing has a threaded bore 33 therein which is closed during the treatment by any suitable means such as a bolt 34 held in sealing relation by a washer 35 and nut 36 threaded on its outer end. A removable master cover plate 31 is bolted to the casing, and has lowered as by a crane onto the jack 39, the U- shaped handles 38 serving as a convenient engaging means. The jack 39 is then adjusted to raise the valve and bring the inlet and outlet connections of the valve body in line with the extensions 5 and I of the fixed and movable heads respectively. A gasket is inserted between the valve and the face of extension 5 and the nut I5 is rotated by means of bar I5 to bring the movable extension I into proper position with the other end of the valve passageway. A

gasket is then inserted between the face of the extension I and the valve and fluid is turned into the hydraulic cylinder 2| to draw the piston rod 23 downwardly and expand the toggle link connection I! and I6 thereby securing the valve between the fixed and movable heads 2 and 3 respectively; It will be noted that the valve body, so disposed, is substantially unconfined and capable of almost unrestricted deformation. Liquid under pressure is then admitted through the pipe 29 and the pressure is maintained for a period of several minutes. Under this pressure stresses are set up in the valve walls which cause the valve body, or at least portions thereof, to take a permanent deformation. The pressure is maintained until no further deformation occurs and is then relieved, the valve removed from the apparatus, and the, seat 21 is smoothly machined to the required dimensions. A plug machined to the proper size is then inserted in the valve seat 21 and if desired, is lapped into' position to produce an accurate fit. The valve is then assembled and is ready for final test.

It will be understood that the method of the present invention may be carried out in other scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come withinthe meaning and range of equivalency of the claims ,are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In the manufacture of plug valves, the method which comprises subjecting a substantially unconfined plug valve casing having its seat in a roughly finished state to an internal pressure substantially in excess of its rated working pressure and suflicient to cause permanent deformation of portions only thereof and maintaining said pressure until substantial permanent deformation of the casing has occurred, and thereafter machining the seat to its final dimension.

2. In the manufacture of plug valves having cast steel bodies, the method which comprises subjecting a substantially unconfined valve body with its seating surface unfinished to an internal pressure substantially in excess of its rated working pressure and sufficient to cause permanent deformation of portions only thereof and maintaining said pressure until substantial deforma tion of the casing has occurred, and thereafter machining and lapping the valve seat to its final dimension. A I

3. In the manufacture of irregular casings, such as valve casings designed to retain substances under pressure, having internal machined surfaces and which are to be subjected to test pressures in excess of rated working pressures, the method which comprises subjecting a substantially unconfined incompletely machined casing to internal pressure substantially in excess of the test pressure to be used, said internal pressure be ing sumcient to cause permanent localized distortionin portions of the casing, maintaining said internal pressure until substantially no further distortion occurs, removing said internal pressure, and machining the internal surface to final size. v

4. In the manufacture of irregular casings, such as valve casings designed to retain substances under pressure and having internal machined surfaces, the method which comprises subjecting a substantially unconfined incompletely machined casing to internal pressure substantially in excess ofthe pressure to which the casing is to be subjected after it is completely machined, said internal pressure being sufllcient cess of any pressure to which the valve may be subjectedduring test or normal operation after the. casing has been completely 'machined, said internal pressure .beingsufiicient to cause permanent localized distortipn in portions of said casing, maintaining said internal pressure until substantially no further distortion occurs, removing said internal pressure and machining said surfaces to final size.

6. In the manufacture of valves having machined seating surfaces, the method which comprises subjecting a substantially unconfined incompletely machined valve body to an internal pressure of about 133 per cent to 150 per cent in excess of its rated working pressure while simultaneously gauging the defamation of the casing caused by said pressure, maintaining said pressure until substantially permanent localized deforma-tion occurs, removing said pressure, and thereafter finishing the seating surfaces to final dimensions. 5

7. In, the manufacture of valves having machined seating surfaces and which are to be subjected to test pressures in excess of rated working pressures, the method which comprises subjecting a substantially unconfined valve .body to internal prestressing pressure about 16% per cent to 25 per cent in excess of the final test pressure to which the valve is to be subjected, said prestressing pressure causing permanent localized distortion in portions of said body, maintaining said prestressing pressure until substantially no further distortion occurs, removing said prestressing pressure and machining the seating surfaces to final size.

i SVEN J. 'NORDB'I'ROM. 

